I do not see any dotted line in single window mode... is it a
reminescent of an old GIMP-2.7 single window test mode?

The version I used is that of the git repository on 2012-04-08.
I just installed gimp-2.8.0-RC1, which was released also on the same
date, and still I have these dotted lines in single-window mode!

I've never seen dotted lines, but there's a thin vertical strip with a
simulated grip half-way down. I think it may depend on your gtk+ theme.

Liam

I use opensuse-12.1 with KDE-4.4.4

I use Ubuntu 12.04 with Unity.

It could change in:

...depending on your system and you current theme loaded, you may notice
some dotted lines, just two handles, some other graphics or simply
nothing, separating the image area from the lateral panels. Anyway,
visible or not, clicking and draggingon those areas, you can change the
panel width inside the GIMP main window...

I do not see any dotted line in single window mode... is it a
reminescent of an old GIMP-2.7 single window test mode?

The version I used is that of the git repository on 2012-04-08.
I just installed gimp-2.8.0-RC1, which was released also on the same
date, and still I have these dotted lines in single-window mode!

I've never seen dotted lines, but there's a thin vertical strip with a
simulated grip half-way down. I think it may depend on your gtk+ theme.

Liam

I use opensuse-12.1 with KDE-4.4.4

I use Ubuntu 12.04 with Unity.

It could change in:

...depending on your system and you current theme loaded, you may notice
some dotted lines, just two handles, some other graphics or simply
nothing, separating the image area from the lateral panels. Anyway,
visible or not, clicking and draggingon those areas, you can change the
panel width inside the GIMP main window...